So what exactly do you do when a guy comes from out of nowhere and claims to know you, and almost everything you've been up to, with such intimate precision? Not trust the guy, of course!

But last week's Fringe went deeper than that. While the Fringe Division battled a different kind of shapeshifter -- one that could blend in much better than the last ones we've seen -- they also grappled with the return of Peter, or at least to them, a guy who claims to be Peter. An uneasy alliance, there, because at the moment they clearly need him (and his shapeshifter knowledge), and yet they aren't willing to face the deeper implications of everything he knows.

So we have Olivia acting suspiciously around him, going as far as asking Lincoln out. And we have Walter, who believes that all of this is a trick being played on him, and that he doesn't deserve to be happy after all he's done to (inadvertently) ruin both universes. In other words, last week's Fringe was pretty loaded. Cue John Noble explaining a few things about how Walter sees things. John?

Time loop anomalies? Sounds a lot like what the Observers deal with. Sounds like the sort of thing the Observers watch for and try to iron out before it affects everything. Sounds like it could explain how Peter, despite being wiped out of existence by the First People's machine -- and both versions of him dying in the new timeline -- returned, with all his memories from a timeline that shouldn't exist now. But I could be wrong.

So, could tonight's Fringe clear things up for us a bit? Or will the guest appearances of Stephen Root and Romy Rosement (aka Finn's mom on Glee) just serve as a metaphor of sorts between Peter, Olivia and Walter's new state of affairs? Fringe is back tonight from 9pm on Fox.